From a point of view of protection of a driver and/or a passenger in a car, an air bag apparatus which is a passenger protection apparatus has conventionally widely been used. The air bag apparatus is equipped for the purpose of protecting a driver and/or a passenger against shock caused at the time of collision of a vehicle, and it receives a body of a driver or a passenger with an air bag serving as a cushion, as the air bag is expanded and developed instantaneously at the time of collision of the vehicle.
The gas generator is equipment which is incorporated in this air bag apparatus, an igniter therein being ignited in response to power feed through a control unit at the time of collision of a vehicle to thereby burn a gas generating agent with flame caused by the igniter and instantaneously generate a large amount of gas, and thus expands and develops an air bag.
Gas generators of various structures are available. A disc type gas generator of which outer geometry is in a substantially short columnar shape is available as a gas generator suitably used for an air bag apparatus on a driver's seat side, and a cylinder type gas generator of which outer geometry is in a substantially long columnar shape is available as a gas generator suitably used for a side air bag apparatus, a curtain air bag apparatus, an air bag apparatus on a passenger's seat side, and a knee air bag apparatus.
It is important for a gas generator to burn a gas generating agent continually in a stable manner at the time of activation of an igniter. In order to burn the gas generating agent continually in a stable manner, the gas generating agent should be placed in a prescribed high-pressure environment. Therefore, the gas generator is designed to narrow a plurality of gas discharge openings provided in the housing to a desired size so that a pressure in a space in the housing is raised to a considerable level at the time of activation of the igniter.
It is important for the gas generator to reliably achieve sealing of a space in the housing from an external space in order to prevent the gas generating agent accommodated in the housing or an enhancer agent loaded in the housing as necessary for burning the gas generating agent from absorbing moisture. If the gas generating agent or the enhancer agent absorbs moisture, desired output characteristics may not be obtained at the time of activation of the gas generator.
Therefore, such a construction has generally been adopted for a conventional gas generator that a gas discharge opening is narrowed to a necessary opening diameter so as to sufficiently raise a pressure in the space in the housing at the time of activation and a sealing tape made of a metal is applied to the housing so as to close the gas discharge opening (see, for example, Japanese Patent Laying-Open No. 2001-219810 (PTD 1)).